Separation of alpha emitting species from plating baths

Patent metadata

Field	Value
Publication number	US-10167568-B2
Application number	US-201815944030-A
Country	US
Kind code	B2
Filing date	Apr 3, 2018
Priority date	Nov 24, 2015
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

Abstract

A non alpha controlled alloy that includes a metal and an alpha emitting material is utilized as a plating anode to selectively plate the metal upon a plating cathode. The metal may be selectively plated by pulse plating the non alpha controlled alloy with current control to suppress plating of the alpha emitting material upon the plating cathode. The metal may also be selectively plated by pulse plating the non alpha controlled alloy with potential control to suppress plating of the alpha emitting material upon the plating cathode. The metal may also be selectively plated by plating out the alpha emitting material upon a filtering cathode.

First claim

What is claimed is:

1. A plating method comprising:
creating a circuit between an unpurified plating anode and a plating cathode immersed within a plating bath, wherein the unpurified plating anode comprises a metal and an alpha emitting material, and wherein the plating cathode comprises a semiconductor wafer;
dissolving the metal and the of alpha emitting material into the plating bath; and
selectively plating the metal upon the semiconductor wafer to reduce an alpha particle emissivity of the metal to less than 2α/cm 2 /1000 hours.

2. The method of claim 1 , further comprising:
suppressing plating of the alpha emitting material upon the semiconductor wafer.

3. The method of claim 2 , wherein suppressing plating the alpha emitting material upon the semiconductor wafer further comprises:
increasing agitation of the plating bath and increasing the concentration of the metal near the semiconductor wafer.

4. The method of claim 3 , wherein increasing the concentration of the metal near the semiconductor wafer comprises:
pulsing current through the circuit to increase the concentration of the metal near the semiconductor wafer.

5. The method of claim 2 , wherein suppressing plating of the alpha emitting material upon the semiconductor wafer further comprises:
controlling potential across the circuit to a plating potential that which the alpha emitting material does not plate upon the semiconductor wafer.

6. The method of claim 5 , further comprising:
measuring a reference potential within the plating bath at a plating surface of the semiconductor wafer.

7. The method of claim 2 , wherein suppressing plating of the alpha emitting material reduces an alpha particle emission rate of the semiconductor wafer.

8. A plating method comprising:
creating a first circuit between a plating anode and a plating cathode immersed within a plating bath, the plating anode comprising a metal and an alpha emitting material, the plating cathode comprising a semiconductor wafer;
creating a second circuit between a filtering anode and a filtering cathode immersed within the plating bath; and
reducing the alpha emitting material from the plating bath by plating the alpha emitting material upon the filtering cathode.

9. The method of claim 8 , wherein the filtering anode comprises a surface area ten times relative to a surface area of the filtering cathode.

10. The method of claim 8 , wherein the plating bath is comprised within a plating tool reservoir.

11. The method of claim 8 , wherein the first circuit is located within a plating tool reservoir and the second circuit is located within a plating tool filter.

12. The method of claim 8 , wherein a current is passed through the first circuit to plate the metal upon the semiconductor wafer at a first deposition rate and wherein a pulse and reverse pulse current is passed through the second circuit to plate the alpha emitting material upon the filtering cathode at a second deposition rate, the second deposition rate twice the first deposition rate.

13. The method of claim 8 , wherein reducing the alpha emitting material from the plating bath increases the concentration of metal plated upon the semiconductor wafer and reduces an alpha particle emission rate of the semiconductor wafer.

Assignees

• IBM

Inventors

• Arvin Charles L
• Gordon Michael S

Classifications

• H10P74/207

  Electrical properties, e.g. testing or measuring of resistance, deep levels or capacitance-voltage characteristics · CPC title

• H10P14/47

  Electrolytic deposition, i.e. electroplating; Electroless plating · CPC title

• H10W72/01235

  by plating, e.g. electroless plating or electroplating · CPC title

• H10W72/012

  of bump connectors, dummy bumps or thermal bumps · CPC title

• H01L2224/11462

  Electricity · mapped topic